Process for catalytic co2 desorption and supported catalyst for said process

Abstract

The present invention relates to a process for CO2 desorption in an overall CO2 absorption / desorption procedure. The present invention in particular relates to a process and a system for the catalytic CO2 desorption steps, in the presence of at least one supported Zr- based catalyst. The present invention also relates to a suitable supported Zr-based catalyst for the CO2 desorption process, and to methods for preparing such a catalyst.

Description

[0001] PROCESS FOR CATALYTIC CO2DESORPTION AND SUPPORTED CATALYST FOR SAID PROCESS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a process for CO2desorption in an overall CO2absorption / desorption procedure. The present invention in particular relates to a process and a system for the catalytic CO2desorption steps, in the presence of at least one supported Zr- based catalyst. The present invention also relates to a suitable Zr-based catalyst for the CO2desorption process, and to methods for preparing such a catalyst.

[0004] BACKGROUND

[0005] The rapidly increasing carbon dioxide (CO2) concentration in the atmosphere has caused great climate changes. From the latest report of the Intergovernmental Panel on Climate Change (IPCC), limiting warming to close to 1.5°C or even 2°C will be beyond reach, unless there are immediate, rapid, and large-scale reductions in CO2emissions. However, the risks and costs of non-fossil energy alternatives such as nuclear, biomass, solar energy, etc., cannot meet current energy demands. Additionally, any rapid changes to non-fossil energy sources, even if possible, would result in large disruptions to the existing energy supply infrastructure with substantial consequences to the global economy. The fossil fuel energy is believed to remain the dominant energy source from the Energy Information Administration. Under that premise, CO2capture and storage (CCS), and CO2capture and utilization (CCU) become promising routes to limit the savagely increasing CO2emission. However, for both routes, CO2capture is always the first step. In order to meet mid-to-long-term CO2reduction targets, it is necessary to develop a cost-effective CO2capture technology.

[0006] For the CO2from power plants, from any other type of fossil-fired furnace to provide high temperature heat or from any other type of fossil carbon combustion into CO2(like steel mills, cement calciners, etc.), one of the dominant CO2emission sources, Post-Combustion Capture (PCC), using amine solvent as a CO2absorber, is the most mature and widely used technology. Moreover, it is believed to be the most promising technology to provide an energy-efficient and timely solution for decreasing CO2emissions from fossil power plants, fossil fired furnaces or fossil carbon combustion. A typical amine-based CO2capture and regeneration process involves the entire absorption-desorption cycle of CO2using amine solvents, as shown in Figure 1. The CO2-containing flue gas stream is introduced into a packed bed absorber column where it flows counter currently as it contacts lean amine, allowing for efficient absorption. After absorption, the rich amine solvent flows through a rich-lean heat exchanger before being introduced into a stripper column for thermal regeneration. In the stripper column, thermal energy such as heated steam, is supplied, for example to the reboiler, to strip out the captured CO2 by increasing the temperature. This free (lean) amine solvent then returns to the absorber column for a new cycle of absorption.

[0007] Typical amine solvents for CO2 capture include primary amines like monoethanolamine (MEA), secondary amines like diethanolamine (DEA), and tertiary amines like methyldiethanolamine (MDEA). The mechanism of CO2 absorption in different amine solvents is shown as follows:

[0008] Primary / secondary amine:

[0009] CO2+ 2R1R2NH 2R1R2NH2++ R^NCOQ-

[0010] Tertiary amine: co2+ R1R2R2N + H2O R1R2R3NH++ HCO3~

[0011] MEA is the most widely used amine solvent because of the tremendous CO2 absorption rate, high capacity, high mass-transfer performance, and low-price properties. The absorption of CO2 in MEA solvent follows a Zwitterion mechanism. One CO2 is absorbed and forms one carbamate (anion) and one neutralizing protonated MEA (cation). Without willing to be bound to any theory, the desorption process consists of a series of chemical step(s) and physical transport steps: first the carbamate has to be decomposed into amine and dissolved CO2, while the protonated amine needs to deprotonated, next the dissolved CO2 moves to the liquidgas interphase and finally the dissolved CO2 escapes from the liquid solvent into the gas phase moving to the top of the stripper column while the solvent moves to the bottom of the stripper column. While the physical transport steps can be enhanced by increasing turbulence and in particular by increasing the liquid-gas interphase area, the carbamate decomposition requires a minimum activation energy to occur. Such minimum activation energy can be attained by using a catalyst that reduces the required activation energy.

[0012] As shown in Figure 2, the desorption route of CO2 from MEA mainly comprises two steps: (1) proton transfer, which includes proton transferring from protonated amine to water and proton transferring from HaO+to carbamate; (2) carbamate breakdown and release of CO2. The proton transfer steps are unfavourable at low temperatures, forcing the industry to run under a high desorption temperature for an acceptable solvent regeneration efficiency. However, the high regeneration temperature (100~140°C) consumes more than 60% of the overall energy cost for PCC, and also causes degradation of amine solvent and corrosion of equipment. Extensive studies have been carried out to reduce the energy cost during the solvent regeneration step of the primary amine. New amine solvents and bi-phasic amine solvents can significantly reduce the energy cost during desorption while maintaining a relatively high CO2 absorption rate. However, they are still economically inefficient due to the high price of the solvent and complex reactor.

[0013] From a catalytic perspective, using a proper catalyst can decrease the activation energy of the carbamate decomposition reaction (or the individual reactions steps of deprotonation of the ammonium cation and the protonation of the carbamate) and hence the reaction rate, boosting the overall CO2 desorption process, thereby decreasing the stripping time and increasing the solvent regeneration efficiency. Moreover, some catalysts allow CO2 desorption at a temperature lower than 100°C, which could significantly reduce the energy consumption and solvent loss.

[0014] WO 2011120138 discloses a method, which applies solid catalysts into the CO2 absorption and desorption process. It was reported that by using an acid catalyst like H-ZSM-5 in the stripper, CO2 desorption from 5 M MEA solvent could be detected at a temperature lower than 50°C. The reason for low-temperature desorption is considered to be the direct donation of the proton from the Bronsted acid (B acid) site of H-ZSM-5 to carbamate. The catalyst performance between the B acid site and the Lewis acid (L acid) site with H-ZSM-5 and y- AI2O3 was also compared. B acid catalysts like H-ZSM-5 showed better performance on CO2 desorption than Lewis acid catalysts like Y-AI2O3 during the CO2 rich stage (temperature ramping stage) but showed poorer performance during CO2 lean stage (isothermal stage). There are many following reports on using solid acid catalysts, like HY, H-Beta, CeSCL / ZrCh, CMK-3-SiC>2, SO427ZrC>2 / SBA-15 for CO2 desorption from amine solvent.

[0015] US2016030880A1 discloses a series of metal oxides which increase the CO2 desorption amount from 3 M MEA. It also used acidic material (metal oxide, zeolites, proton-exchange resins) to help amine regeneration. The metal oxides contained metals from rows 3-5 in the Periodic Table. V2O5, MoOs, WO3, O2O3, MgO, Y-AI2O3, VOx / AhCh, MoOx / AhCh, WOx / AhCh, H-zeolite-Y, proton-exchange resin (Amberlyst 15 (H)) were tested. Among other materials, MoOs showed the best catalytic performance, which caused CO2 desorption to start at 40°C and increased CO2 desorption amount by 27%. However, almost 96% of MoOs dissolved during the reaction. The dissolving amount decreased to 68% after using Y-AI2O3 as support. However, the CO2 desorption amount also decreased. It seems that the improvement of the desorption is highly related to the dissolution of the metal oxide. This increased the difficulties on catalyst separation after the solvent regeneration process, which greatly limited the application for those types of catalysts.

[0016] US20160250591A1 reports TiO(OH)2 as an efficient catalyst for CO2 desorption from amine solvent. TiO(OH)2 can drastically improve the CO2 desorption rate of a CCh-saturated 20 wt % MEA solution by 100% during the temperature ramping stage at a low temperature of 88°C, which was much higher than the previous catalysts investigated.

[0017] US2010 / 209323A1 discloses DeNOx catalysts for the reduction of NOx compounds and porous catalyst support materials are provided. The inventive catalysts comprise an active metal catalyst component and mixed TiCh / ZrCh porous support particles synthesized through a precipitation method in the presence of a sulphate compound, that comprise a) a crystalline phase comprising titanium dioxide and / or a titanium / zirconium mixed oxide, b) an amorphous phase comprising zirconium, and c) a small amount of one or more metal oxide(s) or metalloid oxide(s) deposited on the amorphous outer layer. The inventive catalysts exhibit superior activity and ammonia selectivity.

[0018] According to the reported results, using solid catalyst has already shown some improvement on low-temperature CO2 desorption from amine solvent but still cannot meet the application requirement due to the limitation of poor catalytic performance or catalyst dissolution problems. A solid catalyst with better and stable catalytic performance is strongly needed to decrease the energy consumption of the amine regeneration process for PCC.

[0019] Therefore, there is a need for improved catalysts and improved processes for CO2 desorption.

[0020] SUMMARY OF THE INVENTION

[0021] It has now been found that the above objectives can be attained either individually or in any combination by using the specific and well-defined processes and catalysts as disclosed herein.

[0022] The Applicants have developed a supported Zr-based catalyst, preferably comprising ZrO(OH)2, and a method for preparing said catalyst,. This catalyst shows advantageous properties when applied in a CO2 desorption process. For example, the catalytic activity of catalysts according to the invention, and embodiments thereof, is far greater than any previously reported catalyst. The catalytic activity increases with increase in catalytic loading. Supporting the active catalytic phase, being Zr-based catalyst on a solid support, preferably a high surface area support, allows to expose more active sites to the CCh-laden solvent and hence may reduce the cost of expensive catalytic material. The catalytic action is confirmed as the catalytic activity is maintained over cycles. The present invention, and embodiments thereof, also allows for a reduction in size of the desorption column leading to lower CAPEX. The present invention, and embodiments thereof, also allows for a reduction in temperature of CO2 desorption, which in turn leads to lower energy requirements (OPEX). The present invention, and embodiments thereof, also allows to reduce the cost of regeneration of solvents in the absorption process.

[0023] More specifically, the Applicants have found that a supported Zr-based catalyst according to the invention, or embodiments thereof, allows to increase the CO2 desorption rate under low temperature in the solvent regeneration process for the amine-based CO2 Post-Combustion Process. The catalyst material preferably comprises a specific O:Zr atomic ratio. The catalyst material preferably comprises ZrO(OH)2, and / or is synthesized under a preferred pH with a preferred basic precipitating agent. The catalyst material can be deposited directly on solid catalyst support, preferably a high surface area support under a preferred pH with a preferred basic precipitating agent. Reference to “preferred pH” may mean that the final pH of the synthesis process while during the synthesis process the pH can in particular be lower than the preferred pH.

[0024] The Applicants have demonstrated that a supported Zr-based catalyst according to the invention can boost the CO2 desorption rate at a low temperature. The synthesis method influences the ratio of acid and basic hydroxyl groups and the surface charge property, which is demonstrated herein to cause an additional improvement in catalytic performance.

[0025] The catalysts prepared according to the invention, or embodiments thereof, can be used in MEA solvent and other amines in a CO2 capture plant. The boosting of CO2 desorption rate with the catalysts makes it possible for the solvent regeneration process to run under a lower temperature which can significantly decrease the energy cost of PCC and prevent the amine solution from degradation and evaporation. The catalyst is stable and insoluble in amine solvent, which makes it easy to be separated and regenerated. Furthermore, the catalyst can be deposited on a structured support (inert packing) to replace traditional packing, or can be shaped in solid structure to replace traditional packing.

[0026] In a first aspect, the present invention provides a method for preparing a supported Zr-based catalyst for CO2 desorption, the catalyst preferably comprising ZrO(OH)2. The method preferably comprises the steps of: providing a slurry comprising a solid catalyst support and a soluble Zr source and a solvent, thereby preparing a synthesis slurry; providing a basic precipitating agent; and, precipitating a Zr-based catalyst on the solid catalyst support, by adding the basic precipitating agent to the synthesis slurry, thereby obtaining a supported Zr-based catalyst.

[0027] The method is preferably characterized in that the final pH of the synthesis solution is at least 3 and at most 8, preferably at least 4 and at most 7, for example about 5. By this it is meant that the basic precipitating agent is added until the pH of the synthesis slurry is at least 3 and at most 8, preferably at least 4 and at most 7, for example about 5.

[0028] In some embodiments, the solid catalyst support is a porous solid catalyst support, preferably a mesoporous solid catalyst support. Preferably, the solid catalyst support is a silicate or an aluminosilicate.

[0029] In some preferred embodiments, the supported Zr-based catalyst (excluding the solid catalyst support) comprises Zr, O, and H. Preferably, the O:Zr atomic ratio is at least 2.1 , preferably at least 2.2, for example at least 2.3, for example at least 2.4, for example at least 2.5, for example at least 2.6, for example at least 2.7, for example at least 2.8, for example at least 2.9. In some embodiments, the O:Zr atomic ratio is at least 3.0, for example at least 3.5, for example at least 4.0.

[0030] In some preferred embodiments, the supported Zr-based catalyst comprises ZrO(OH)2. Preferably, the supported Zr-based catalyst comprises at least 60% by weight ZrO(OH)2 compared to the total weight of the supported Zr-based catalyst (excluding the solid catalyst support), preferably at least 70%, preferably at least 80%, preferably at least 90%, for example at least 95%, for example at least 98%, for example at least 99%.

[0031] In some preferred embodiments, the basic precipitating agent is a hydroxide, preferably selected from the group comprising: NaOH, NH4OH (NHa*H2O), and KOH. Preferably, the basic precipitating agent is NaOH.

[0032] In some preferred embodiments, the Zr source is selected from the group comprising: zirconylnitrate, zirconyl-halides, zirconyl-sulphate, zirconium-alkoxides or zirconium halides, preferably ZrO(NOa)2.

[0033] In some preferred embodiments, the method further comprises the step of: calcining the supported Zr-based catalyst at a calcination temperature Tc. Preferably, the calcination temperature Tc is at most 400°C, preferably at most 350°C, preferably at most 300°C, preferably at most 250°C, preferably at most 200°C, preferably at most 150°C, preferably at most 100°C.

[0034] In a second aspect, the present invention provides a supported Zr-based catalyst for CO2 desorption, prepared using the method according to the first aspect, and embodiments thereof. Preferably, the O:Zr atomic ratio is at least 2.1. Preferably, the supported Zr-based catalyst comprises ZrO(OH)2.

[0035] (Preferred) embodiments of the first aspect are also (preferred) embodiments of the second aspect, and vice versa.

[0036] In some preferred embodiments, the ratio of acidic OH to basic OH of the supported Zr-based catalyst is at least 0.1 and at most 1.3, preferably at least 0.2 to at most 1.2, preferably at least 0.5 to at most 1 .2, preferably at least 0.8 to at most 1.1 , preferably about 1 .0.

[0037] In some preferred embodiments, the supported Zr-based catalyst has a surface charge Zeta potential, preferably under pH 9.5, of at least -25 mV, preferably at least -15 mV, preferably at least -5 mV, for example at least 0 mV, for example at least 5 mV.

[0038] In some preferred embodiments, the supported Zr-based catalyst comprises other metals, preferably selected from the group comprising: Hf, Ce, or Zn. In some preferred embodiments, the purity of Zr compared to the other metals deposited on the catalyst support in the supported Zr-based catalyst is at least 80%, preferably at least 85%, preferably at least 90%, preferably at least 95%.

[0039] In some preferred embodiments, the supported Zr-based catalyst comprises other metals, preferably selected from the group comprising: Hf, Ce, or Zn. In some preferred embodiments, the molar fraction of Zr compared to the other metals deposited on the catalyst support in the supported Zr-based catalyst is at least 80 mol%, preferably at least 85 mol%, preferably at least 90 mol%, preferably at least 95 mol%.

[0040] In a third aspect, the present invention provides a process for CO2 desorption from an amine solvent. The process preferably comprises the steps of: providing an CCh-containing amine solution comprising CO2 absorbed in an amine solvent; providing a supported Zr-based catalyst according to the second aspect; supplying to the CCh-containing amine solution to the supported Zr-based catalyst; optionally, heating the amine solution comprising the supported Zr-based catalyst to a desorption temperature Td; and, desorbing CO2 from the amine solution comprising the supported Zr-based catalyst during a contact time.

[0041] (Preferred) embodiments of the second aspect are also (preferred) embodiments of the third aspect, and vice versa.

[0042] In some preferred embodiments, the supported Zr-based catalyst acts as a non-soluble heterogeneous catalyst.

[0043] In some preferred embodiments, the amine solvent comprises a primary amine, secondary amine, or tertiary amine. Preferred amines are alkanolamines that have at least one hydroxyl group and one amino group. The hydroxyl group serves to reduce vapor pressure and increases the solubility in water, while the amine group provides the necessary alkalinity in aqueous solutions to promote the reaction with acid gases. Preferably, the primary amine solvent comprises monoethanolamine (MEA) or 2-amino-2-methyl-1 -propanol (AMP), diglycolamine (DGA); preferably monoethanolamine (MEA). Preferred secondary alkanolamines are diethanolamine (DEA) and diisopropanolamine (DI PA). Tertiary amines such as triethanolamine (TEA) or methyldiethanolamine (MDEA) are sometimes used. Primary and secondary amines are very reactive as they form carbamates by direct reaction with CO2 by Zwitterion mechanism. As these amines require two amine groups to make a carbamate, they exhibit limited capacity to absorb CO2. Other used primary or secondary amines are piperazine, aminosiloxanes and amino-acids. On the other hand, tertiary amines can only form a bicarbonate ion and protonated amine by the base-catalysed hydration of CO2 due to their lack of the necessary N— H bond. Hydration is slower than the direct reaction by carbamate formation and, hence, tertiary amines show low CO2 absorption rates.

[0044] In some preferred embodiments, the CO2 stripping is done in a continuous manner; preferably at a contact time or weight hourly space velocity (WHSV) between the circulating solvent and the catalytic material of between 0.01 to 1000 h’1, for example 34 h’1, for example between 0.01 to 100 h-1(meaning in case of 1 h-1that a stream of one kg per hour of solvent is treated over one kg of catalytic material).

[0045] In a fourth aspect, the present invention provides a process for CO2 absorption and desorption.

[0046] Preferably, the process comprises the steps of: absorbing CO2 in an amine solvent, thereby obtaining a CCh-containing amine solution; and, desorbing CO2 from the CCh-containing amine solution using the process according to the third aspect, or embodiments thereof, thereby regenerating the amine solvent.

[0047] (Preferred) embodiments of the third aspect are also (preferred) embodiments of the fourth aspect, and vice versa.

[0048] In a fifth aspect, the present invention provides the use of a supported Zr-based catalyst, preferably a catalyst according to the second aspect, or embodiments thereof, in a process according to the third or fourth aspect, or embodiments thereof.

[0049] (Preferred) embodiments of the second, third, or fourth aspect are also (preferred) embodiments of the fifth aspect, and vice versa.

[0050] BRIEF DESCRIPTION OF THE FIGURES

[0051] Figure 1 illustrates a carbon capture process schematic.

[0052] Figure 2 shows the reaction route for CO2 desorption from a primary and secondary amine solvent.

[0053] Figure 3 illustrates a schematic lab-scale CO2 desorption apparatus.

[0054] Figure 4 illustrates (A) CO2 loading concentration versus reaction time and (B) a kinetic study during the isothermal stage in 5 M CO2-saturated MEA with different catalysts.

[0055] Figure 5 illustrates (A) CO2 loading concentration versus reaction time, (B) a kinetic study during the isothermal stage in 5 M CO2-saturated MEA with different loading amounts of ZrO(OH)2, and (C) the relationship between catalytic reaction rate constant (kCAT) and catalyst loading amount.

[0056] Figure 6 illustrates (A) a scheme for solvent recycled experiment, (B) CO2 loading concentration versus reaction time, and (C) a kinetic study of kCAT during the isothermal stage in recycled MEA solvent without solid catalysts.

[0057] Figure 7 illustrates the CO2 desorption in 5 M CCh-saturated MEA solution for a 168 h reaction with and without ZrO(OH)2. Figure 8 illustrates (A) a scheme of two catalyst regeneration methods: wash recycled and directly recycled, (B) CO2 loading concentration versus reaction time in 5 M CCh-saturated MEA with ZrO(OH)2 regenerated by different methods.

[0058] Figure 9 illustrates (A) CO2 loading concentration versus reaction time in 5 M CCh-saturated MEA with ZrO(OH)2 synthesized under different pH, and (B) the relationship between kCAT and the synthesis pH of ZrO(OH)2.

[0059] Figure 10 illustrates (A) CO2 loading concentration versus reaction time and (B) a kinetic study during the isothermal stage in 5 M CCh-saturated MEA with ZrO(OH)2 synthesized by different methods.

[0060] Figure 11 illustrates a thermogravimetric analysis (TGA) result of the ZrO(OH)2 catalyst under N2 atmosphere.

[0061] Figure 12 illustrates the relationship between ZrO(OH)2 synthesis pH and density of basicity -OH, acidity -OH and total -OH.

[0062] Figure 13 illustrates the relationship between kCAT and the Acidity -OH / Basicity -OH ratio.

[0063] Figure 14 illustrates (A) CO2 loading concentration versus reaction time, and (B) a kinetic study during the isothermal stage in 5 M CO2-saturated MEA with ZrO(OH)2 calcined under different temperatures.

[0064] Figure 15 illustrates the XRD results of commercial ZrO2 and different-temperature-calcined ZrO(OH)2.

[0065] Figure 16 illustrates (A) CO2 loading concentration versus reaction time and (B) a kinetic study during the isothermal stage in 5 M CO2-saturated MEA with different MZrO(OH)2 catalysts.

[0066] Figure 17 illustrates the relationship between kCAT and Zeta potential of different ZrO(OH)2 based catalysts at pH 9.3.

[0067] Figure 18 illustrates (A) CO2 loading concentration versus reaction time and (B) a kinetic study during the isothermal stage in 2.5 M CO2-saturated AMP with and without different catalyst.

[0068] Figure 19 illustrates a scheme for a continual CO2 desorption reactor. Figure 20 illustrates a zoomed in section of the scheme for a continual CO2 desorption reactor illustrated in Figure 19.

[0069] Figure 21. illustrates (A) CO2 loading concentration versus reaction time and (B) a kinetic study during the isothermal stage in 5 M CCh-saturated MEA with Supported Zr-based catalysts.

[0070] Figure 22 show the effect of the temperature of the calcination on the supported Zr-based catalyst.

[0071] DETAILED DESCRIPTION OF THE INVENTION

[0072] When describing the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0073] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0074] In the following passages, various aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements, or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of", "consists" and "consists of".

[0075] As used in the specification and the appended claims, the singular forms "a", "an," and "the" include plural referents unless the context clearly dictates otherwise. By way of example, "a step" means one step or more than one step.

[0076] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art.

[0077] The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

[0078] The term "about" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / -10% or less, preferably + / -5% or less, more preferably + / -1% or less, of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" refers is itself also specifically, and preferably, disclosed.

[0079] The terms “wt%”, “vol%”, or “mol%” refers to a weight percentage of a component, a volume percentage of a component, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, which includes the component.

[0080] When describing the present invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0081] Whenever herein the composition of the supported Zr-based catalyst is described, the composition or weight of the solid catalyst support is not included, unless otherwise specified. Preferred features, embodiments, and uses of this invention are set herein below. Each embodiment of the invention so defined may be combined with any other embodiment unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. Hereto, the present invention is in particular captured by any one or any combination of one or more of the below embodiments, with any other aspect and / or embodiment.

[0082] In a first aspect, the present invention provides a method for preparing a supported Zr-based catalyst for CO2 desorption, the catalyst preferably comprising ZrO(OH)2. The method preferably comprises the steps of: providing a slurry comprising a solid catalyst support and a soluble Zr source and a solvent, thereby preparing a synthesis slurry; providing a basic precipitating agent; and, precipitating a Zr-based catalyst on the solid catalyst support, by adding the basic precipitating agent to the synthesis slurry, thereby obtaining a supported Zr-based catalyst.

[0083] The method is preferably characterized in that the pH of the synthesis solution is at least 3 and at most 8, preferably at least 4 and at most 7, for example about 5. In some embodiments, the pH of the synthesis solution is at least 3, preferably at least 4, for example at least 5. In some embodiments, the pH of the synthesis solution is at most 8, preferably at most 7, for example at most 6.

[0084] A catalyst prepared this way was found to provide a significant improvement on CO2 desorption properties without significant dissolution, as illustrated in the example section. More specifically, the present synthesis method influences the ratio of acid and basic hydroxyl groups and the surface charge property, which is demonstrated herein to cause an additional improvement in catalytic performance.

[0085] In some embodiments, the solvent in the slurry is water or an oxygenated organic, such as methanol. Preferably, the solvent in the slurry is water.

[0086] In some preferred embodiments, the supported Zr-based catalyst comprises Zr, O, and H. Preferably, the O:Zr atomic ratio is at least 2.1 , preferably at least 2.2, for example at least 2.3, for example at least 2.4, for example at least 2.5, for example at least 2.6, for example at least 2.7, for example at least 2.8, for example at least 2.9, for example about 3.0. In some embodiments, the O:Zr atomic ratio is at least 3.0, for example at least 3.5, for example at least 4.0. In some embodiments, the O:Zr atomic ratio is at most 5.0, for example at most 4.9, for example at most 4.8, for example at most 4.7, for example at most 4.6, for example at most 4.5, for example at most 4.4, for example at most 4.3, for example at most 4.2, for example at most 4.1 , for example about 4.0. In some embodiments, the O:Zr atomic ratio is at least 2.1 and at most 5.0, for example at least 2.2 and at most 4.9, for example at least 2.3 and at most 4.8, for example at least 2.4 and at most 4.7, for example at least 2.5 and at most 4.6, for example at least 2.6 and at most 4.5, for example at least 2.7 and at most 4.4, for example at least 2.8 and at most 4.3, for example at least 2.9 and at most 4.2, for example at least 2.9 and at most 4.1 , for example about 3.5. In some embodiments, the O:Zr atomic ratio is at least 2.1 and at most 4.0, for example at least 2.2 and at most 3.9, for example at least 2.3 and at most 3.8, for example at least 2.4 and at most 3.7, for example at least 2.5 and at most 3.6, for example at least 2.6 and at most 3.5, for example at least 2.7 and at most 3.4, for example at least 2.8 and at most 3.3, for example at least 2.9 and at most 3.2, for example at least 2.9 and at most 3.1.

[0087] A catalyst with this atomic ratio was found to provide a significant improvement on CO2 desorption properties.

[0088] The O:Zr atomic ratio is herein defined as the bulk ratio and can be measured by the weight loss of the catalyst between 170°C to 800°C assuming the weight loss is from the loss of hydroxyl groups forming H2O, and the rest of the solids are ZrC>2. The weight loss can be measured by Thermalgravimetric analysis (TGA) tested under N2 flow and a temperature rate of between 5 to 20°C / min, preferably 10°C / min, assuming all the weight decrement after a temperature of 180°C forms water and the final solid species above 600-800°C is considered ZrO2.

[0089] In some preferred embodiments, the supported Zr-based catalyst comprises ZrO(OH)2. Preferably, the supported Zr-based catalyst comprises at least 60% by weight ZrO(OH)2 compared to the total weight of the supported Zr-based catalyst, preferably at least 70%, preferably at least 80%, preferably at least 90%, for example at least 95%, for example at least 98%, for example at least 99%; excluding the support.

[0090] A catalyst with this atomic structure was found to provide a significant improvement on CO2 desorption properties, as illustrated in the example section.

[0091] With preference, the Zr-based catalyst is supported on a solid catalyst support. Preferably, said solid catalyst support has a high specific surface area.

[0092] In some embodiments, the solid catalyst support is a particulate solid catalyst support. Preferably, suitable particulate solid catalyst supports comprise carbon-containing materials like silicon carbide, petroleum coke, black carbon, activated carbon, char and / or graphite and / or carbon nanotubes, and any mixture thereof.

[0093] In some embodiments, suitable particulate solid catalyst supports are refractory oxides such as alumina (AI2O3), silica (SiCh), titania (TiCh), ceria (CeCh), zirconia (ZrCh), magnesia (MgO), yttria (Y2O3), hafnia (HfCh), lanthania (La20s), and any mixture thereof, more preferably alumina, silica, ceria, zirconia, magnesia, and any mixture thereof. A typical example of an amorphous mixed oxide is ASA (amorphous silica-alumina).

[0094] In some embodiments, the solid catalyst support comprises a crystalline mixed oxide, preferably selected from the list comprising: one or more oxides having a cubic fluorite structure optionally being at least partially substituted with one or more lower-valent cations, preferentially selected from Sm, Gd, Y, Sc, Yb, Mg, Ca, La, Dy, Er, Eu; and / or one or more ABCh-perovskites with A and B tri-valent cations, optionally being at least partially substituted in A position with one or more lower-valent cations, preferentially selected from Ca, Sr, or Mg, and comprising at least one of Ni, Ga, Co, Cr, Mn, Sc, Fe and / or a mixture thereof in B position; and / or one or more ABOs-perovskites with A bivalent cation and B tetra-valent cation, optionally being at least partially substituted with one or more lower-valent cations, preferentially selected from magnesium (Mg), scandium (Sc), yttrium (Y), neodymium (Nd) or ytterbium (Yb) in the B position or with a mixture of different B elements in the B position; and / or. one or more A2B2O?-pyrochlores with A trivalent cation and B tetra-valent cation optionally being at least partially substituted in A position with one or more lower-valent cations, preferentially selected from Ca or Mg, and comprising at least one of Sn, Zr and Ti in B position. one or more AB2O4-spinel with A divalent cation and B tri-valent cation (for example MgAhO4, CaAhO4, BaAhO4, SrAhO4, FeAhO4, and ZnAI2O4) comprising at least one of Al or Fe in B position. one or more hydrotalcite, a double layered lamellar clay, comprising brucite-like positively charged layers, with an anionic layer sandwiched between them with general formula [Alli-xBlllx(OH)2]x+[Cn-]x / n yH2O (for example g6Al2(OH)16CO3-4H2O) with A divalent cation and B tri-valent cation.

[0095] In some embodiments, suitable particulate solid catalyst supports are microporous or mesoporous oxides such as molecular sieves, including silica-alumina, silica-boria, silica- germania, alumina-phosphate, silica-alumina-phosphate zeolites, and any mixture thereof. Examples of such molecular sieves are MFI (ZSM-5, silicalite-1 , boralite C, TS-1), MEL (ZSM- 11 , silicalite-2, boralite D, TS-2, SSZ-46), clinoptilolite, MSA (mesoporous silica-alumina, MCM-41 , MCM-48, SBA-15, SBA-16), FER (Ferrierite, FU-9, ZSM-35), MTT (ZSM-23), ZSM- 21 , ZSM-42, ZSM -57, MWW (MCM-22, PSH-3, ITQ-1 , MCM-49), TON (ZSM-22, Theta-1 , NU-10), EUO (ZSM-50, EU-1), MFS (ZSM-57), ZSM- 48, MTW, MAZ, BETA, FAU (zeolite X, Y or SAPO-37), LTL, MOR, zeolite Omega, AFI (SAPO-5), AFO (SAPO-41) and AEL (SAPO- 11).

[0096] In some embodiments, said solid catalyst support further comprises a specific surface area ranging between 5 m2 / g and 1000 m2 / g as determined by N2 adsorption measurement, more preferably between 50 m2 / g and 900 m2 / g, even more preferably between 100 m2 / g and 800 m2 / g, most preferably between 200 m2 / g and 700 m2 / g.

[0097] In some embodiments, the supported Zr-based catalyst may have different shapes according to the location where it is best applied: a power-like solid material (typically having particle size of less than 0.1 millimetre) used in an agitated or stirred reactor vessel that can be operated batch-wise or continuously, a shaped solid material (typically having particle size of more than 0.1 millimetre) comprising crushed irregular particles, spherical particles, solid or open pellet, solid or open rods (extrudates), solid or open trilobed, solid or open quadrilobed shapes, honeycomb shapes, etc. Optionally, the power-like solid material can be circulated with the amine solvent between the absorption and the stripper column. In case of shaped solid materials, the shaped solid material is located in fixed bed type of reactor sections. It is a preferred method of the present invention to operate the CO2 stripping in a continuous manner. The supported Zr-based catalyst may be used in different locations of the stripping section of a CCS unit: in the feed line supplying the rich solvent from the heat exchanger to the stripper column, inside the stripper column on active area of the trays, in the downcomer of the tray or as layered sections within a packed column or both, in the line between the bottom of the stripper column to the reboiler, in the reboiler or as a parallel reactor to the stripper column (withdrawing a liquid stream from the stripper column to be sent to the parallel reactor while the product is reinjected into the stripper column).

[0098] In some embodiments, the solution comprising a precipitating agent comprises at least 1.00 M and at most 1.50 M, for example about 1.25 M precipitating agent.

[0099] In some preferred embodiments, the basic precipitating agent is a hydroxide, preferably selected from the group comprising: NaOH, Na2COs, NaHCCh, (NH^CCh, NH4HCO3, NH4OH (NH3*H2O), K2CO3, KHCOa.or KOH. Preferably, the basic precipitating agent is NaOH. In some embodiments, the solution comprising a Zr source, used to prepare the slurry, comprises at least 2.00 M and at most 4.00 M, for example about 3.00 M Zr source.

[0100] In some preferred embodiments, the Zr source is zirconyl-nitrate, zirconyl-halides, zirconylsulphate, zirconium-alkoxides or zirconium halides.

[0101] In some preferred embodiments, the Zr source is ZrO(NOa)2. ZrO(NOa)2 is a common Zr source, and it may be easier to form ZrO(OH)2 compared to Zr(NOa)4.

[0102] In some preferred embodiments, the catalytic support concentration in the slurry comprises at least 1 weight percent and at most 50 weight percent of catalytic support, for example about 10 weight percent.

[0103] In some preferred embodiments, the solid catalyst support concentration in the slurry comprises at least 1 weight % to at most 50 weight %, preferably at least 2 weight% to at most 30 weight %, preferably at least 3 weight% to at most 20 weight %, preferably at least 4 weight% to at most 10 weight %, of solid catalyst support, for example about 5 weight %.

[0104] In some embodiments, the synthesis of the supported Zr-based catalyst is prepared by dripping the solution comprising a precipitating agent into the slurry comprising a Zr source and the solid catalyst support under stirring. This allows the final pH to be easier controlled. Furthermore, dripping the slurry comprising a Zr source and the solid catalyst support into the solution comprising a precipitating agent might irreversibly form a sediment closer to ZrC>2 in a basic environment.

[0105] In some embodiments, a co-precipitation method is used.

[0106] In some embodiments, the amount of active Zr-based catalyst on the solid catalyst support in the final catalyst is preferably between 1 and 50 weight percent of zirconium in the final catalyst, meaning that 100 gram of supported Zr-based catalyst comprises between 1 and 50 grams of zirconium, more preferably between 5 and 35 weight percent of zirconium and most preferable between 10 and 20 weight percent of zirconium (10 weight percent zirconium in the final catalyst corresponds to about 15,5 weight percent as ZrO(OH)2 and 50 weight percent of zirconium corresponds to 77 weight percent as ZrO(OH)2).

[0107] In some preferred embodiments, the method further comprises the step of: calcining the supported Zr-based catalyst at a calcination temperature Tc.

[0108] Preferably, the calcination temperature Tc is at most 400°C, preferably at most 350°C, preferably at most 300°C, preferably at most 250°C, preferably at most 200°C, preferably at most 150°C, preferably at most 100°C. It was found that a calcination step at too high temperatures removed the OH groups and reduced the catalyst to ZrO2, thereby severely reducing the catalytic activity, as illustrated in the example section.

[0109] In a second aspect, the present invention provides a Zr-based catalyst for CO2 desorption, prepared using the method according to the first aspect, and embodiments thereof. Preferably, the O:Zr atomic ratio is at least 2.1 or other values as described herein. Preferably, the supported Zr-based catalyst comprises ZrO(OH)2, preferably at percentages as described herein.

[0110] (Preferred) embodiments of the first aspect are also (preferred) embodiments of the second aspect, and vice versa.

[0111] Such a catalyst was found to provide a significant improvement on CO2 desorption properties without significant dissolution, as illustrated in the example section.

[0112] In some preferred embodiments, the ratio of acidic OH to basic OH in the supported Zr-based catalyst is at least 0.1 and at most 1.3, preferably at least 0.2 to at most 1.2, preferably at least 0.5 to at most 1 .2, preferably at least 0.8 to at most 1.1 , preferably about 1 .0.

[0113] Controlling the ratio of acidic OH to basic OH was found to provide a significant improvement on CO2 desorption properties, as illustrated in the example section.

[0114] The ratio of acidic OH to basic OH is preferably measured by Thermogravimetric Analysis (TGA), for example as conducted on a TGA Q500 from TA Instruments. The TGA may be performed under a 10 mL / min N2 atmosphere, with a temperature ramping from 50°C to 150°C for 30 min to make sure all free water is released, and then to 800°C. The temperature ramping rate may be 10°C / min.

[0115] In some preferred embodiments, the supported Zr-based catalyst remains in an amorphous phase upon heating / calcining in ambient / inert until 200-300°C. The inventors have surprisingly found that the best-performing catalysts do not show the tetragonal crystalline t-ZrO2 phase upon heating / calcining in ambient / inert until 200-300°C, but remain in an amorphous phase, whereas inferior catalysts do give clear formation of the t-ZrO2 phase (as measured using classic state of the art powder X-ray diffraction analysis, for example as illustrated in the example section) upon the same thermal treatment. In some preferred embodiments, the supported Zr-based catalyst comprises at most 20.0 wt% of the tetragonal crystalline t-ZrO2 phase, preferably at most 10.0 wt%, preferably at most 5.0 wt%, preferably at most 2.0 wt%, preferably at most 1.0 wt%, preferably essentially no tetragonal crystalline t-ZrO2 phase, after heating / calcining in ambient / inert until 200-300°C. In some preferred embodiments, the supported Zr-based catalyst has a surface charge Zeta potential, preferably under pH 9—10, of at least -25 mV, preferably at least -15 mV, preferably at least -5 mV, for example at least 0 mV, for example at least 5 mV.

[0116] Catalysts with such a high surface charge were found to provide improved CO2 desorption properties, as illustrated in the example section.

[0117] The Zeta potential is preferably measured on a NanoPlus HD with an Auto-Titrator from Particulate Systems. Typically, 40 mg well-grinded sample powder may be mixed with 40 g ultrapure water, followed by a 20 min ultrasonic treatment. The finely dispersed sample solution may be used for the testing. The Zeta potential may be tested under a pH of 9.3 ±0.2. 0.1 M HCI and 0.1 M NaOH may be used for pH adjustment.

[0118] In some preferred embodiments, the supported Zr-based catalyst comprises other metals, preferably selected from the group comprising: Hf, Ce, or Zn. Other metals than Zr might be used for reasons of cost and / or stability. In some preferred embodiments, the purity or molar fraction of Zr compared to the other metals in the supported Zr-based catalyst is at least 80 mol%, preferably at least 85 mol%, preferably at least 90 mol%, preferably at least 95 mol%. Such catalysts were found to also provide suitable catalytic activity.

[0119] In a third aspect, the present invention provides a process for CO2 desorption from an amine solvent. The process preferably comprises the steps of: providing an CCh-containing amine solution comprising CO2 absorbed in an amine solvent; providing a supported Zr-based catalyst according to any one of claims 6 to 9; supplying to the CCh-containing amine solution to the supported Zr-based catalyst; optionally, heating the amine solution comprising the supported Zr-based catalyst to a desorption temperature Td; and, desorbing CO2 from the amine solution comprising the supported Zr-based catalyst during a contact time.

[0120] (Preferred) embodiments of the second aspect are also (preferred) embodiments of the third aspect, and vice versa.

[0121] The present invention allows to reduce the cost of regeneration of solvents in the absorption / desorption process. In some preferred embodiments, the supported Zr-based catalyst acts as a non-soluble heterogeneous catalyst. The catalyst is typically stable and insoluble in amine solvent, which makes it easy to be separated and regenerated.

[0122] In some preferred embodiments, the amine solvent comprises a primary amine, secondary amine, tertiary amine, or mixtures thereof. Examples of suitable amines include but are not limited to: monoethanolamine (MEA), 2-amino-2-methyl-1 -propanol (AMP), diethanolamine (DEA), diglycolamine (DGA), methyldiethanolamine (MDEA), piperazine (PZ), ammonia, amines, alkanolamines, aminosiloxanes, amino-acids, derivatives and / or combinations thereof. Preferably, the amine solvent comprises monoethanolamine (MEA) or 2-amino-2- methyl-1 -propanol (AMP), preferably monoethanolamine (MEA).

[0123] In some embodiments, the amine solvent comprises a combination of two or more amines, for example AMP with PZ as a co-solvent. A combination of amines can increase absorption rate and cyclic capacity to reduce energy of regeneration (heat duty), application of high amine solution concentration and minimized degradation.

[0124] An AMP / PZ (3 M / 1 .5 M) ratio is considered to be the preferred ratio. The proper ratio of AMP / PZ can increase the absorption rate and the cyclic capacity while avoiding the precipitation of PZ.

[0125] In some embodiments, the amine solvent is present in the amine solution at a molar concentration of at least a 1 M to at most a 10 M, preferably of at least a 2 M to at most an 8 M, preferably of at least a 4 M to at most a 6 M, for example at about a 5 M concentration. These concentrations were found to provide optimal results, as illustrated in the example section.

[0126] In some embodiments, the supported Zr-based catalyst is provided in a concentration of at least 1 .0 g to at most 8.0 g, preferably of at least 2.0 g to at most 6.0 g, preferably of at least 2.5 g to at most 4.0 g, for example about 3.0 g Zr-based catalyst per 100 mL amine solution to be treated in a time frame from one to ten hours.

[0127] These amounts were found to provide optimal results, as illustrated in the example section.

[0128] In some embodiments, the desorption temperature Td is at most 500 K, preferably at most 450 K, preferably at most 400K, preferably at most 380 K, preferably about 361 K.

[0129] The present invention has the significant advantage that the desorption temperature can be kept low. The boosting of CO2 desorption rate with the catalysts makes it possible for the solvent regeneration process to run under a lower temperature which can significantly decrease the energy cost of PCC and prevent the amine solution from degradation and evaporation.

[0130] In some preferred embodiments, the CO2 stripping is done in a continuous manner at a contact time or weight hourly space velocity (WHSV) between the circulating solvent and the catalytic material of between 0.01 to 1000 h-1(meaning in case of 1 IT1that a stream of one kg per hour of solvent is treated over one kg of catalytic material).

[0131] These contact times were found to provide optimal results, as illustrated in the example section.

[0132] In a fourth aspect, the present invention provides a process for CO2 absorption and desorption. Preferably, the process comprises the steps of: absorbing CO2 in an amine solvent, thereby obtaining a CCh-containing amine solution; and, desorbing CO2 from the CCh-containing amine solution using the process according to the third aspect, or embodiments thereof, thereby regenerating the amine solvent.

[0133] (Preferred) embodiments of the third aspect are also (preferred) embodiments of the fourth aspect, and vice versa.

[0134] The present invention allows to reduce the cost of regeneration of solvents in the absorption / desorption process.

[0135] In some embodiments, the process is a batch process. In some more preferred embodiments, the process is a continuous process.

[0136] In some embodiments, the process further comprises the step of: recycling the supported Zr-based catalyst into the process.

[0137] The catalyst of the present invention has the advantage that it can be easily recycled, particularly since the catalyst typically acts as a non-soluble heterogeneous catalyst.

[0138] In some embodiments, the step of recycling the supported Zr-based catalyst comprises the step of: directly recycling the supported Zr-based catalyst and amine solvent into the process, by using the supported Zr-based catalyst and amine solvent in a reabsorption step without separation.

[0139] In some embodiments, the step of recycling the supported Zr-based catalyst comprises the step of: removing the supported Zr-based catalyst from the amine solvent, preferably through filtration, centrifuging, or a hydrocyclone;

[0140] - washing the supported Zr-based catalyst with water; optionally, recovering the supported Zr-based catalyst through filtration, centrifuging or a hydrocyclone.

[0141] Optionally, drying the supported Zr-based catalyst; and, adding the optionally dried catalyst to an amine solvent.

[0142] In a fifth aspect, the present invention provides the use of a supported Zr-based catalyst, preferably a catalyst according to the second aspect, or embodiments thereof, in a process according to the third or fourth aspect, or embodiments thereof.

[0143] (Preferred) embodiments of the second, third, or fourth aspects are also (preferred) embodiments of the fifth aspect, and vice versa.

[0144] In some embodiments, the supported Zr-based catalyst can have different shapes according to the location where it is best applied: a power-like solid material (typically having particle size of less than 0.1 millimetre) used in an agitated or stirred reactor vessel that can be operated batch-wise or continuously, a shaped solid material (typically having particle size of more than 0.1 millimetre) comprising crushed irregular particles, spherical particles, solid or open pellet, solid or open rods (extrudates), solid or open trilobed, solid or open quadrilobed shapes, honeycomb shapes, etc. Optionally, the power-like solid material can be circulated with the amine solvent between the absorption and the stripper column. In case of shaped solid materials, the shaped solid material is located in fixed bed type of reactor sections. It is a preferred method of the present invention to operate the CO2 stripping in a continuous manner. The supported Zr-based catalyst can be used in different locations of the stripping section of a CCS unit: in the feed line supplying the rich solvent from the heat exchanger to the stripper column, inside the stripper column on active area of the trays, in the downcomer of the tray or as layered sections within a packed column or both, in the line between the bottom of the stripper column to the reboiler, in the reboiler or as a parallel reactor to the stripper column (withdrawing a liquid stream from the stripper column to be sent to the parallel reactor while the product is reinjected into the stripper column).

[0145] Use of a supported Zr-based catalyst as described herein allows for a reduction in size of the desorption column leading to lower CAPEX. Use of a supported Zr-based catalyst as described herein also allows for a reduction in temperature of CO2 desorption, which in turn leads to lower energy requirements (OPEX), and / or less solvent degradation. For example, desorption at lower temperatures allows for less degradation of the amine(s). EXAMPLES

[0146] The following examples serve to merely illustrate the invention and should not be construed as limiting its scope in any way. While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the scope of the invention.

[0147] Experimental Methods

[0148] An experimental apparatus for solvent regeneration (CO2 desorption) is shown in Figure 3. It consists of a 250 mL round-bottom flask equipped with a thermometer, a heater controlled by a temperature controller, a condenser, a magnetic field stirrer. For a typical CO2 desorption experiment run, 150 mL 5 M MEA solution with initial CO2 loading (0.52 mol / mol) and 3 g catalyst is mixed in the reactor under a 500 mL / min N2 flow from the top of the condenser. Then the solution was heated to 361.1 K in 50 ± 5 min and kept constant for 180 min with a stirring rate of 500 rpm. The time when the solution reached 361.1 K is noted as 0 min. For a long time (168 h) CO2 desorption experiment, 6 g ZrO(OH)2 is used in 150 mL 5 M MEA. The CO2 concentration of the solution is analysed by Chittick equipment with the average absolute relative deviation less than 5%. Typically, 500 pL CO2 loaded amine solution was added to the flask by a pipette, then 1 mL of 1.5 M H2SO4 was injected into the solution under violent stirring. The volume of released CO2 is noted to further calculate the CO2 concentration of the sample. Every sample was tested three times, and the average value was adopted.

[0149] The catalysts are evaluated in two aspects: CO2 deposition amount during the temperature ramping stage and the catalytic reaction rate constant (kcA-r).

[0150] The kcAi- is calculated as follows: kcAT—koverall " kblank koveraii is the overall reaction rate constant calculated through the CO2 concentration of 0 min, 30 min, 60 min, 90 min, 120 min and 180 min after the temperature gets stable (isothermal stage), kbiank is calculated from the changes of the CO2 concentration in MEA solvent without any catalysts during the first 3 h desorption in the isothermal stage. Without specific description, the value of kbiank is considered to be -1.3 *10-4min-1.

[0151] X-ray powder diffraction (XRD) was conducted on a high-throughput STOE STADI P Combi diffractometer in the transmission mode with focusing Ge(111) monochromatic X-ray inlet beams (A=1.5406 A, Cu Ka source). Thermogravimetric analysis (TGA) was conducted on TGA Q500 from TA Instruments. Typically, the TGA was performed under a 10 mL / min N2 atmosphere, with a temperature ramping from 50°C to 150°C for 30 min to make sure all free water is released, and then to 800°C. The temperature ramping rate was 10°C / min.

[0152] Zeta potential was tested on NanoPlus HD with an Auto-Titrator from Particulate Systems. Typically, 40 mg well-grinded sample powder was mixed with 40 g ultrapure water, followed by a 20 min ultrasonic treatment. The finely dispersed sample solution was used for the testing The Zeta potential was tested under a pH of 9.3 ±0.2. 0.1 M HCI and 0.1 M NaOH were used for pH adjustment.

[0153] N2 absorption measurements were performed using Micromeritics Instruments Tristar 3000 at 77 K. The samples were degassed under N2 flow at 250 °C for 6 h prior to measurement. The relative nitrogen pressure varied between 0.01 and 0.99 (p / pO).

[0154] The O:Zr ratio for different pH synthesized Zr-based catalyst samples prepared according to the invention were found to be: 4.27, 4.50, 4.85, 3.39, 2.85, and 2.49 as measured by the TGA method. It is assumed that the weight loss is due to water release only from which the O:Zr ratio is estimated, and this oxygen reflects the sum of hydroxyl groups and hydration or adsorbed water.

[0155] Example 1 : CO2 desorption performance with different catalysts

[0156] The performance of different catalysts is shown in Figure 4 and Table 1. The O:Zr ratio for these catalysts was between 3:1 and 5:1. Compared with Blank, all three of H-ZSM-5, TiO(OH)2 and ZrO(OH)2 show improvement on CO2 desorption amount during the temperature ramping stage, while ZrO(OH)2 shows 150% improvement on CO2 desorption amount compared to H-ZSM-5 and TiO(OH)2. After the temperature stabilizes, there is no noticeable improvement on CO2 desorption with H-ZSM-5, but TiO(OH)2 and ZrO(OH)2 still show a significant improvement in CO2 desorption rate. A kinetic study on the isothermal stage found that the kcAT value for H-ZSM-5 is almost 0, while ZrO(OH)2 shows the highest kcAT value of - 3.1*10'4min-1, which is 2.4 times the value of TiO(OH)2. MoOa shows a very high increment of CO2 desorption amount at the temperature ramping stage but a lower CO2 desorption rate than ZrO(OH)2 at the isothermal stage. The kcAT for MoOa is only -1.8*1 O'4min-1, which means that the catalytic effect of MoOs is only about 58% of ZrO(OH)2. To be noted, MoOs is completely dissolved after the temperature reaches 88°C, but there is no significant dissolution for ZrO(OH)2. Considering the k0Veraii for blank MEA solvent is -1.3 *10-4min-1, using ZrO(OH)2 provides a 238% improvement on the reaction rate constant of the CO2 desorption from MEA at 88°C.

[0157] Table 1

[0158] CO2 desorption Performance with Different Catalysts Summary

[0159] CO2 desorption kcAT

[0160] Catalyst amount (mmol) (*10'4min'1)

[0161] Blank 41.0 0

[0162] H-ZSM-5 43.6 -0.06

[0163] TiO(OH)248.9 -1.3±0.2

[0164] MoO356.0 -1.8

[0165] ZrO(OH)248.9 -3.1±0.2

[0166] Reaction condition: 3 g of catalyst, 150 mL CCh-saturated 5 M MEA, N2 flow of 0.5 L / min from the top of the condenser, 88°C. The CO2 desorption amount is calculated at the end of the temperature ramping stage.

[0167] Example 2: CO2 desorption performance for different catalyst amounts

[0168] CO2 desorption performance with different ZrO(OH)2 amounts is shown in Figure 5 and Table 2. The CO2 desorption amount during the temperature ramping stage increased with the amount of the catalyst. The KCAT in the isothermal stage and the catalyst amount show a linear relationship when the catalyst amount is below 4 g. However, when the catalyst amount increased to 6 g, the KCAT is no longer increased linearly but relatively lower due to the mass transfer limitation.

[0169] Table 2

[0170] CO2 desorption Performance with Different ZrO(OH)2 Loading Amount ZrO(OH)2 CO2 desorption kcAT

[0171] Amount (g) amount (mmol) (*10'4min'1)

[0172] 0 41.0 0

[0173] 1.5 47.6 -1.8±0.2

[0174] 2 48.9 -2.2±0.3

[0175] 3 48.9 -3.1±0.2

[0176] 4 50.0 -3.6±0.4

[0177] 6 52.8 -4.7±0.4

[0178] Reaction condition: 150 mL CCh-saturated 5 M MEA, N2 flow of 0.5 L / min from the top of the condenser, 88°C. The CO2 desorption amount is calculated at the end of the temperature ramping stage.

[0179] To confirm that the active sites of ZrO(OH)2 do come from the solid phase instead of the solubilized species, the solid phase ZrO(OH)2 was removed from the MEA solution by centrifuge after a typical CO2 desorption reaction, and the remaining MEA solution was collected, re-absorbed with CO2, and went for another desorption test without any catalyst, noted as "solvent recycle". The experimental scheme and results are shown in Figure 6. The removal of the catalyst ceases the catalytic effect as the desorption performance shows no noticeable difference with the blank. The desorption rate constant decreased by more than 90% than that of ZrO(OH)2.

[0180] In a long-time desorption experiment (Figure 7), ZrO(OH)2 improved almost 70% CO2 desorption amount compared with blank at 24 h. After that, due to the thermodynamic limitation, the CO2 desorption rate with ZrO(OH)2 was suppressed, and the CO2 concentration of the solution approached the blank and finally reached a similar level after 168 h. This also indicates that the CO2 desorption with ZrO(OH)2 is not a stoichiometric reaction but a catalytic reaction.

[0181] A catalyst regeneration test was also carried out in two ways: water washed regeneration and directly recycled. The scheme for the two methods is shown in Figure 8A. For washed recycled, the spent ZrO(OH)2 is washed with water, centrifuged, and dried under 100°C overnight, then used in a new CO2 desorption test. For directly recycled, the reacted mixture (lean MEA solution and ZrO(OH)2) directly went for a re-absorption followed by the desorption process. As shown in Figure 8B, both directly recycled and water washed recycled ZrO(OH)2 show similar CO2 desorption performance as the fresh ZrO(OH)2. The result indicate that ZrO(OH)2 is not a one-time catalyst and can be easily recycled.

[0182] Example 3: Effect of synthesis pH on catalyst synthesis

[0183] A typical ZrO(OH)2 is synthesized through a precipitation method. NaOH solution was dripped into a ZrO(NOa)2 solution until pH reached 5 under violent stirring. After ageing for 3 h, the sediment was centrifuged and washed three times, then dried at 100°C for 48 h. The outstanding catalytic performance of ZrO(OH)2 on CO2 desorption from the amine solvent is due to the carefully controlled synthesis process and the finely designed surface property.

[0184] By changing the amount of the basic precipitating agents, the synthesis pH of ZrO(OH)2 can be easily controlled. As shown in Figure 9 and Table 3, ZrO(OH)2 synthesized under different pH showed vastly different catalytic performance.

[0185] Table 3

[0186] CO2 desorption Performance

[0187] With ZrO(OH)2 Synthesized Under Different pH

[0188] ZrO(OH)2 CO2 desorption KCAT synthesis pH amount (mmol) (*10'4min'1)

[0189] Blank 41.0 0

[0190] 3 52.8 -0.7

[0191] 4 46.2 -2.4±0.2

[0192] 5 48.9 -3.1±0.2

[0193] 6 47.6 -2.2±0.3

[0194] 7 46.2 -1.8

[0195] 8 41.0 -1.0

[0196] 12 38.3 0

[0197] Reaction condition: 3 g of catalyst, 150 mL CCh-saturated 5 M MEA, N2 flow of 0.5 L / min from the top of the condenser, 88°C. The CO2 desorption amount is calculated at the end of the temperature ramping stage. The relationship between KCAT and the synthesis pH shows a volcano curve, where KCAT reaches the maximum with 3.1*1 O'4min-1at a synthesis pH of 5. When the synthesis pH went either higher or lower, an apparent drop in kcAT appears. To be noted, ZrO(OH)2 synthesized under lower pH like pH 3 shows a high CO2 desorption amount during the temperature ramping stage with very low catalytic effect (kcAT= -0.7*1 O'4min-1), which indicated that the improvement might be due to the remaining acid during the synthesis process.

[0198] Example 4: Effect of synthesis method on catalyst synthesis

[0199] This example compares the catalytic performance of ZrO(OH)2 synthesized by a method according to an embodiment of the invention, and ZrO(OH)2 synthesized from a reported synthesis method for metal hydroxyl oxide.

[0200] Following the reported method of synthesis of high-performance TiO(OH)2, ZrO(OH)2 (iso) catalysts were synthesized. Zirconium isopropoxide was added into deionized water with a molar ratio of H2O:Zr being 1400:1 , followed by stirring for 4h. The precipitate powder was filtered, rinsed three times with deionized water and ethanol, then dried at 100°C for ~10h.

[0201] The ZrO(OH)2 can also be synthesized through a hydrothermal method. ZrO(NOa)2 was mixed in a water-ethanol solvent, and kept at 80°C and circulated for 2 h. The precipitate powder was then filtered, rinsed three times with deionized water, and dried at 100°C for ~10h. The dried powder is noted as ZrO(OH)2 (hydro).

[0202] Table 4

[0203] CO2 desorption Performance

[0204] With ZrO(OH)2 Synthesized With Different Methods

[0205] CO2 desorption kcAT

[0206] Catalysts amount (mmol) (*10'4min'1)

[0207] Blank 41.0 0

[0208] TiO(OH)248.9 -1.3±0.2

[0209] ZrO(OH)248.9 -3.1±0.2

[0210] ZrO(OH)2(iso) 47.6 -1.6 ZrO(OH)2(hydro) 51.5 0.9

[0211] Reaction condition: 3 g of catalyst, 150 mL CO2-saturated 5 M MEA, N2flow of 0.5 L / min from the top of the condenser, 88°C. The CO2desorption amount is calculated at the end of the temperature ramping stage.

[0212] The catalytic performance of ZrO(OH)2synthesized with different methods for CO2desorption is shown in Table 4 and Figure 10. Although ZrO(OH)2(hydro) shows the highest CO2desorption amount during the temperature ramping stage, it shows a KCAT of 0.9 * 10 '4min-1, which has an even negative effect on the CO2desorption rate during the isothermal stage. ZrO(OH)2(iso) shows a similar improvement on CO2desorption amount as ZrO(OH)2does. During the temperature ramping stage, the KCAT value for ZrO(OH)2(iso) is -1.6*1 O'4min-1, which is only 51% of ZrO(OH)2but still higher than that of TiO(OH) (1.3*1 O'4min-1). The result further proves the advantage of the current synthesis methods and shows that the ZrO(OH)2itself is more suitable for CO2desorption than TiO(OH)2.

[0213] Example 5: Effect of hydroxyl groups

[0214] The hydroxyl groups for ZrO(OH)2are believed to show either acidity or basicity depending on the binding type. Mono-binding -OH can be considered as weak bases. It has lower binding energy with Zr and can be removed at a lower temperature (below 400°C). While for bridged- binding -OH groups, they have a stronger binding with Zr and can be considered weak B acid. The removal temperature for bridged-binding -OH is relative higher (400~600°C).

[0215] Since the hydroxyl group is releasing as H2O with the raising of the temperature, the hydroxyl groups amount can be quantified by TGA. A typical TGA result for ZrO(OH)2is shown in Figure 11 . The water released between 200°C ~400°C is considered to be from weak bonding -OH (basic -OH), and the water released between 400°C to 600°C is considered to come from strong bonding -OH (acidic -OH).

[0216] The hydroxyl group density for ZrO(OH)2synthesized under different pH values is shown in Figure 12. It can be seen that the synthesis pH has a significant influence on the -OH group. When the synthesis pH increased from 3 to 5, the total density of the hydroxyl group only slightly decreased from 25.7 mmol / g to 23.3 mmol / g, with a slight increase of basic -OH (from 10.8 to 11.6 mmol / g) and a decrease of acidic -OH (from 14.9 to 12.1 mmol / g). When the synthesis pH further increased from 5 to 7, both total -OH density and acidic -OH decreased significantly, but basic -OH remained almost not changed. By further increasing the pH to 12, the drop on both types of -OH density occurred.

[0217] A volcano curve relationship between KCAT and the basic / acid -OH ratio is shown in Figure 13. The kcAT reaches the top when the basic and acidic -OH ratio is close to 1.0. The results indicate that there is a synergetic effect between acidic and basic -OH; thus controlling the basic and acidic -OH ratio of the catalysts may be one of the critical factors for the high- performance ZrO(OH)2.

[0218] To further prove the importance of the hydroxyl group of the catalyst, ZrO(OH)2 is calcined from 200°C to 600°C to partly remove the -OH group from ZrO(OH)2. From Figure 14 and Table 5, it can be seen that the CO2 desorption amount at the temperature ramping step decreased with the increasing calcination temperature. However, ZrO(OH)2 calcined at 200°C and 300°C only shows a slight decrease in catalytic performance. By further increasing the calcining temperature to 400°C, the kcAT further drops to -1.3*1 O'4min-1. The XRD results (Figure 15) show that below 400°C calcination, ZrO(OH)2 remained amorphous and after a 400°C-calcination, the ZrO(OH)2 crystalized and formed f-ZrO2 with a crystal size of 30nm. However, compared to commercial ZrO2, ZrO(OH)2 (400°C) shows a twofold kcAT. The better performance of the ZrO(OH)2 compared with ZrC>2 may be due to the higher density of the hydroxyl groups, which makes it a better catalyst than ZrC>2. On the other hand, by calcining ZrO(OH)2 under a temperature of 300°C, a more stable catalyst can be achieved with only a slight drop in catalytic performance. The O:Zr ratio for ZrO(OH)2 (400°C) was 2.17:1 , while for the other catalysts it was higher than 3:1.

[0219] Table 5

[0220] CO2 desorption Performance With ZrO(OH)2 Calcined under different temperature

[0221] Catalysts CO2 desorption kcAT

[0222] (calcination temperature) amount (mmol) (*10'4min'1)

[0223] Blank 41.0 0

[0224] ZrO(OH)248.9 -3.1 ±0.2

[0225] ZrO(OH)2(200°C) 48.9 -2.3

[0226] ZrO(OH)2(300°C) 47.6 -2.0 ZrO(OH)2(400°C) 43.6 -1.4

[0227] ZrC>2 (commercial) 42.3 -0.6

[0228] Reaction condition: 3 g of catalyst, 150 mL CO2-saturated 5 M MEA, N2flow of 0.5 L / min from the top of the condenser, 88°C. The CO2desorption amount is calculated at the end of the temperature ramping stage.

[0229] Example 6: Catalytic Performance of Mixed Metal Hydroxyl Oxide

[0230] Mixed Metal hydroxyl oxides are investigated based on the ZrO(OH)2. Typically, 10% of the metal nitrate is mixed with Zirconium precursor, followed by the same synthesis method with ZrO(OH)2. The catalyst is noted as 10%MZrO(OH)2, (M=Hf, Ce, Zn); alternatively the following formulation may be used: Mo.iZro.90(OH)2.

[0231] As shown in Figure 16 and Table 6, 10%ZnZrO(OH)2showed 25% improvement on CO2desorption amount compared with the blank, which had a 10% improvement to ZrO(OH)2. However, the KCAT of 10%ZnZrO(OH)2is only -1.6*1 O'4min-1, which is lower than 10%HfZrO(OH)2(-1.9*1 O'4mim1), and 10%CeZrO(OH)2(-2.3*1 O’4min'1). ZrO(OH)2still shows the highest kcAT of -3.1*1 O'4min-1. To be noted, even for the lowest kcAT of 10%MZrO(OH)2, which is 10%ZnZrO(OH)2, it still shows a 25% improvement to the kcAT of TiO(OH)2.

[0232] Table 6

[0233] CO2desorption Performance

[0234] With Different MZrO(OH)2

[0235] CO2desorption kcAT

[0236] Catalysts amount (mmol) (*10'4min'1)

[0237] Blank 41.0 0

[0238] ZrO(OH)248.9 -3.1 ±0.2

[0239] 10%HfZrO(OH)248.9 -1.9

[0240] 10%CeZrO(OH)247.6 -2.3

[0241] 10%ZnZrO(OH)251.5 -1.6

[0242] TiO(OH)248.9 -1.3±0.2 Reaction condition: 3 g of catalyst, 150 mL CCh-saturated 5 M MEA, N2 flow of 0.5 L / min from the top of the condenser, 88°C. The CO2 desorption amount is calculated at the end of the temperature ramping stage.

[0243] Example 7: Surface Charge Of the ZrO(OH)2 Based Catalysts

[0244] The surface charge of the ZrO(OH)2 based catalysts are tested through a Zeta potential analyzer under pH 9—10, which is the typical pH of the CO2-MEA solvent during the desorption. The value of Zeta potential reflects the charge property of the particles’ surface. A positive Zeta potential indicates that the particle's surface is positively charged, and the absolute value for the Zeta potential reflects the density of the charges. Figure 17 shows a clear relationship between the KCAT and the Zeta potential of the ZrO(OH)2. The higher the Zeta potential is, the higher the catalytic effect is achieved. The higher Zeta potential results in a higher concentration of carbamate species adsorbed on the surface of the catalyst, which is favourable for the carbamate breakdown step and results in showing a higher catalytic effect.

[0245] Example 7: CO2 desorption performance with ZrO(OH)2 in 2.5 M CCh-Saturated AMP Solution 2-amino-2-methyl-1 -propanol (AMP) has been proposed as a commercially attractive new CO2 absorbent because of its advantages in absorption capacity, absorption rate, degradation resistance, and regeneration energy.

[0246] Table 7

[0247] CO2 desorption Performance

[0248] With and Without Different Catalysts

[0249] CO2 desorption kcAT

[0250] Catalyst amount (mmol) (*10'4min'1)

[0251] Blank 110 0

[0252] TiO(OH)2115 -1.3

[0253] ZrO(OH)2116 -4.6 Reaction condition: 3 g of catalyst, 150 mL CCh-saturated 2.5 M AMP, N2 flow of 0.5 L / min from the top of the condenser, 88°C. The CO2 desorption amount is calculated at the end of the temperature ramping stage.

[0254] To show the CO2 desorption performance with ZrO(OH)2 catalyst in other amine solvents, a CO2 desorption experiment was conducted in a CCh-saturated 2.5 M AMP solution. The CO2 desorption performance is shown in Figure 18 and Table 7. AMP already showed a very high desorption rate without any catalysts. The kbiank of AMP is -4.8 *10’4min-1which is about three times compared with that of MEA. However, ZrO(OH)2 still shows improvement in both the temperature ramping stage and the isothermal stage. And compared with TiO(OH)2 (-1.3*1 O’4min-1), the KCAT of ZrO(OH)2 showed a 250% improvement. The results proved that ZrO(OH)2 does not only work well in MEA solvent, but can also be applied in other amine solvents for boosting the CO2 desorption rate under low temperature.

[0255] Example 8: industrial desorption process

[0256] To simulate the continual desorption process in industry, the catalyst is also tested in a self- built continual reactor (see Figure 19, and a zoomed in section in Figure 20). The CCh-rich amine solution was fed over the catalysts bed from the bottom at a flow rate of 3.4 mL min’1under 85 °C. CO2 released from the amine solution was carried out to the analysis system by N2 flow blowing from the top of the liquid level. The CO2 desorption flowrate is calculated by the intensity of m / z=44 signal from mass spectroscopy (MS). The results were double checked by titrating CCh-lean amine solution.

[0257] The calculation methods are shown as followed:

[0258] The CO2 desorption rate calculated through MS:

[0259] / : CO2 signal intensity from MS

[0260] A: Calibration factors of MS signal (%)

[0261] CO2(%): CO2 concentration (%)

[0262] FN2N2 flow rate (m L / min)

[0263] FCO2released CO2 flow rate (m L / min) The CO2 desorption rate is also checked through titrating liquid samples after reaction, which is calculated as below:

[0264] FcO2=(c^— C0)xFMEA ct: CO2 concentration in the reacted solution (mLco2 / mLco2) cO: CO2 concentration in the fresh solution (mLco2 / mLco2) FMEAFlow rate of MEA solution

[0265] Table 8 shows the results of CO2 desorption rate in continual reactor with different catalysts. The test without catalyst (called blank) contained glass beads of comparable size as that of the catalysts, which showed a relative low CO2 desorption rate by 9.7 mL / min. By using TiO(OH)2, the CO2 desorption rate increased to 21.0 mL / min. The CO2 desorption rate with ZrO(OH)2 is 35.50 mL / min, which showed 266% improvement compared with that of the blank and 69% compared with TiO(OH)2.

[0266] Table 8. CO2 desorption rate and cycling capacity with different catalysts

[0267] CO2 desorption rate

[0268] Catalysts

[0269] (mL / min)

[0270] Blank 9.7

[0271] TiO(OH)221.0

[0272] ZrO(OH)235.50

[0273] Reaction condition: N2: 100 mL / min, CO2 saturated MEA solution flow: 3.4 mL / min, 85 °C, 3 cm catalyst.

[0274] Figures 19 and 20 use following reference numbers: 101 - Liquid sampling; 111 - Rich amine tank; 112 - Lean amine tank; 121 - Pump; 122 - Coriolis circular heat exchanger; 123 - Heated transfer line; 124 - Drain valve; 125 - Heating laboratory bath; 126 - Cold finger trap; 127 - Process cooling water; 128 - Variable vacuum pump; 129 - Flow indicator; 130 - Catalyst; 140 - Mass spectroscopy.

[0275] Example A: Synthesis Methods for Supported Zr-based Catalysts A slurry was prepared by mixing 160 mL 0.3 M ZrO(NOa)2 solution and 5g MCM-41 (Mobil Composition of Matter No. 41) or SiC>2 powder, which was left to stir for 10 minutes followed by an ultrasonic treatment for 15 minutes.

[0276] A 1 .25 M NaOH solution was dripped into the slurry until pH 5 was reached under violent stirring (approximately 45 ml).

[0277] After ageing for 3 h, the sediment was centrifuged and washed three times, then dried at 100°C for 48 h.

[0278] In the case 5 g MCM-41 was used, 8.3 g supported catalyst (Zr-MCM-41) was obtained.

[0279] Example 9: effect of supported catalysts versus soluble catalysts on CO2 desorption ability

[0280] CO2 desorption performance with different catalysts is shown in Figure 21 and Table 9. Figure 21. illustrates (A) CO2 loading concentration versus reaction time and (B) a kinetic study during the isothermal stage in 5 M CCh-saturated MEA with Supported Zr-based catalysts.

[0281] Table 9

[0282] CO2 desorption Performance

[0283] With and Without Different Catalysts r t ivstC°2desorption kCAT y amount (mmol) (*10'4min'1)

[0284] Blank 41.0 0

[0285] TiO(OH)2 48.9 -1.3±0.2

[0286] ZrO(OH)248.9 -3.1±0.2

[0287] Zr-MCM-41 48.9 -3.0±0.1

[0288] Zr-SiO248.9 -2.3

[0289] Reaction conditions: 3 g of catalysts, 150 mL CCh-saturated 5 M MEA, N2 flow of 0.5 L min-1from the top of the condenser, 88 °C.

[0290] As illustrated in Figure 21. and Table 9, supported Zr catalysts Zr-MCM-41 shows a similar kcAT of around -3.0*1 O'4min-1compared with ZrO(OH)2 but using 40% less of Zr. For Zr-SiCh, the kcAT drops to -2.3*1 O'4min-1, but still 76% higher than that of TiO(OH)2 (2.3*1 O'4min-1). The examples showed clear benefits for supported Zr catalyst by reaching the same high catalytic effect with a much less Zr amount. Example 10: Effect of calcination temperature on supported Zr catalysts.

[0291] Table 10

[0292] CO2 desorption Performance With ZrO(OH)2 Calcined under different temperature

[0293] Catalysts CO2 desorption KCAT

[0294] (calcination temperature) amount (mmol) (*10'4min'1)

[0295] Blank 41.0 0

[0296] ZrO(OH)248.9 -3.1±0.2

[0297] ZrO(OH)2(200°C) 48.9 -2.3

[0298] ZrO(OH)2(300°C) 47.6 -2.0

[0299] Zr-MCM-41 48.9 -3.0

[0300] Zr-MCM-41 (200°C) 44.9 -2.1

[0301] Zr-MCM-41 (300°C) 34.7 -1.2

[0302] Reaction conditions: 3 g catalysts, 150 mL CCh-saturated 5 M MEA, N2 flow of 0.5 L min-1from the top of the condenser, 88 °C. Figure 22 and Table 10 show that the temperature had the same impact, on the supported Zr which is a catalytic effect that can be seen below a temperature of 300°C, but the best catalyst is obtained for a temperature treatment at 100 °C.

[0303] Table 11

[0304] N2 physisorption results with supported Zr Catalysts

[0305] Catalysts SBET (m2g-1) Vmeso BJH pore size

[0306] MCM-41 986 0.7 2.6 nm

[0307] Zr-MCM-41 1052 0.61 2.5 nm Table 11 shows the N2 physisorption results show similar surface area for MCM-41 and Zr- MCM-41 , showing limited pore blockage due to Zr deposition. A small decrease in pore size (from 2.6 to 2.5 nm) and mesopore volume (from 0.70 to 0.61 cm3g-1) are indications of a fine coating of Zr-0 on the silica surface.

Claims

CLAIMS1 . A method for preparing a supported Zr-based catalyst for CO2 desorption, the method comprising the steps of: providing a slurry comprising a solid catalyst support and a soluble Zr source and a solvent, thereby preparing a synthesis slurry; providing a basic precipitating agent; and, precipitating a Zr-based catalyst on the solid catalyst support, by adding the basic precipitating agent to the synthesis slurry, thereby obtaining a supported Zr-based catalyst; characterized in that the basic precipitating agent is added until the pH of the synthesis slurry is at least 4 and at most 7, for example about 5; and in that the supported Zr-based catalyst comprises Zr, O, and H, wherein the O:Zr atomic ratio is at least 2.1 ; preferably wherein the O:Zr atomic ratio is measured by the weight loss of the catalyst between 170°C to 800°C assuming the weight loss is from the loss of hydroxyl groups forming H2O, and the rest of the solids are ZrCh; wherein the weight loss is measured by Thermalgravimetric analysis (TGA) tested under N2 flow and a temperature rate of between 5 to 20°C / min, preferably 10°C / min, assuming all the weight decrement after a temperature of 180°C forms water and the final solid species above 600-800°C is considered ZrC>2.

2. The method according to claim 1 , wherein the supported Zr-based catalyst comprises ZrO(OH)2, preferably wherein the supported Zr-based catalyst comprises at least 90% by weight ZrO(OH)2 compared to the total weight of the supported Zr-based catalyst, excluding the solid catalyst support.

3. The method according any one of claims 1 or 2, wherein the solid catalyst support is a porous solid catalyst support, preferably a mesoporous solid catalyst support.

4. The method according to any one of claims 1 to 3, wherein the basic precipitating agent is a hydroxide; and / or wherein the Zr source is selected from the group comprising zirconylnitrate, zirconyl-halides, zirconyl-sulphate, zirconium-alkoxides or zirconium halides, preferably ZrO(NOa)2.

5. The method according to any one of claims 1 to 4, further comprising the step of: calcining the supported Zr-based catalyst at a calcination temperature Tc;wherein the calcination temperature Tc is at most 400°C, preferably at most 350°C, preferably at most 300°C, preferably at most 250°C, preferably at most 200°C, preferably at most 150°C, preferably at most 100°C.

6. A supported Zr-based catalyst for CO2 desorption, prepared using the method according to any one of claims 1 to 5, wherein the O:Zr atomic ratio is at least 2.1 ; preferably wherein the supported Zr-based catalyst comprises ZrO(OH)2.

7. The supported Zr-based catalyst according to claim 6, wherein the ratio of acidic OH to basic OH of the supported Zr-based catalyst is at least 0.1 and at most 1.3; preferably wherein the ratio of acidic OH to basic OH is measured by Thermogravimetric Analysis (TGA), for example as conducted on a TGA Q500 from TA Instruments; and wherein the TGA is performed under a 10 mL / min N2 atmosphere, with a temperature ramping from 50°C to 150°C for 30 min to make sure all free water is released, and then to 800°C at a temperature ramping rate of 10°C / min.

8. The supported Zr-based catalyst according to any one of claims 6 or 7, wherein the supported Zr-based catalyst has a surface charge Zeta potential of at least -25 mV, preferably at least -5 mV; preferably wherein the Zeta potential is measured on a NanoPlus HD with an Auto-Titrator from Particulate Systems, wherein 40 mg well-grinded sample powder is mixed with 40 g ultrapure water, followed by a 20 min ultrasonic treatment to obtain a finely dispersed sample solution for the testing under a pH of 9.3 ±0.2; wherein 0.1 M HCI or 0.1 M NaOH may be used for pH adjustment.

9. The supported Zr-based catalyst according to any one of claims 6 to 8, wherein the supported Zr-based catalyst comprises other metals, preferably selected from the group comprising: Hf, Ce, or Zn; preferably wherein the molar fraction of Zr compared to the other metals in the supported Zr-based catalyst is at least 90 mol%, excluding the solid catalyst support.

10. A process for CO2 desorption from an amine solvent, the process comprising the steps of: providing an CO2-containing amine solution comprising CO2 absorbed in an amine solvent; providing a supported Zr-based catalyst according to any one of claims 6 to 9; supplying to the CO2-containing amine solution to the supported Zr-based catalyst; optionally, heating the amine solution comprising the supported Zr-based catalyst to a desorption temperature Td; and,desorbing CO2 from the amine solution comprising the supported Zr-based catalyst during a contact time.

11. The process according to claim 10, wherein the amine solvent comprises an amine selected from the group comprising: monoethanolamine (MEA), 2-amino-2-methyl-1- propanol (AMP), diglycolamine (DGA), diethanolamine (DEA), diisopropanolamine (DIPA), piperazine, aminosiloxanes, and / or amino-acids; preferably monoethanolamine (MEA).

12. The process according to any one of claims 10 or 11 , wherein the amine solvent is present in the amine solution at a molar concentration of at least a 1 M to at most a 10 M, preferably of at least a 2 M to at most an 8 M, preferably of at least a 4 M to at most a 6 M, for example at about a 5 M concentration.

13. The process according to any one of claims 10 to 12, wherein the desorption is performed in a continuous manner at a weight hourly space velocity between 0.01 and 1000 h’1, preferably between 1 and 100 h’1.

14. A process for CO2 absorption and desorption, comprising the steps of: absorbing CO2 in an amine solvent, thereby obtaining a CCh-containing amine solution; and, desorbing CO2 from the CCh-containing amine solution using the process of any one of claims 10 to 13, thereby regenerating the amine solvent.

15. Use of a supported Zr-based catalyst according to any one of claims 6 to 9, in the process according to any one of claims 10 to 14.

Images